Comparison of Food Intake in Multiple Sclerosis Patients and Healthy Individuals: A Hospital-Based Case-Controlled Study.

Objectives
Nutritional factors affect the incidence, severity of symptoms and progression of multiple sclerosis (MS). However, the role of specific nutritional factors remains largely unknown in MS. We conducted this hospital-based case-controlled study to investigate the association between dietary intake and risk of MS.


Materials & Methods
This study was conducted on 93 MS patients and 94 age-matched controls from Oct 2015 to Sep 2016 in Tehran, Iran. MS was diagnosed based on 2010 McDonald criteria and Brain Magnetic Resonance Imaging. Dietary intake was assessed using a validated semi-quantitative food frequency questionnaire. Odds ratio and 95% confidence interval of MS was calculated in different food groups using multiple logistic regression models adjusted for potentially confounding variables and compared between the two groups.


Results
There was no significant difference between the age (34.62 ±9.68 vs. 33.96±8.75) and BMI (23.96 ±4.07 vs. 24.47 ±4.07) of MS and control group, respectively. Higher intake of processed meat (OR (95% CI))=(2.07(1.18-3.63) and non-processed meat (1.38(1.13-1.68)) were found in the MS group compared with the control.


Conclusion
Higher intake of processed meat and non-processed meat was associated with increased risk of MS. Further studies on the probable role of these nutritional factors in the pathogenesis of MS are suggested.


Introduction
Multiple sclerosis (MS) is a neurodegenerative disease of the central nervous system, with an autoimmune inflammatory process leading to blood-brain barrier disruption, perivascular inflammation, demyelination, axonal damage, and progressive neuronal loss. Precise etiology of MS is not clearly identified yet, though immune dysregulation due to genetic susceptibility and multiple environmental factors might have a role (1,2). Inflammatory and neurodegenerative processes Nutritional factors have an effect on incidence and severity of MS. However, the exact role of specific nutritional factors is not known yet (5).
Higher intake of vitamin D has been correlated with decreased incidence of MS as shown in epidemiological studies (6). A considerable number of controlled clinical trials have failed to be conclusive on the role of diet in MS mainly due to limitations of study design, patient characteristics and the number of samples (7).
There is an increasing incidence of MS in Tehran, Iran, and the prevalence was reported as high as 74 in 100,000 in 2013 (8). "Lifetime use of dietary intervention was reported by 41% of people with MS in a study from Germany" (9) supplements before starting the course of the disease. Patients leaving more than 10 food items of questionnaire blank or having a total energy intake less than 800 Kcal or more than 4200 Kcal were excluded (15). The final study sample included 87 cases and 87 controls after applying the exclusion criteria ( Figure 1).
The study was approved by the medical research Ethics Committee of Shahid Beheshti University of Medical Sciences. Written informed consent was obtained from all study participants.

Assessment of dietary intake
We interviewed all the MS patients and control subjects using structured pretested questionnaires. Energy-adjusted nutrient intakes were calculated to remove variation due to energy, using the residual method (19). For data with normal distribution the independent sample t-test and for data not normally distributed, the Mann-Whitney test was conducted to compare differences between the mean dietary intake of micronutrients between the two groups of MS patients and healthy controls. We also divided food items into 13 food groups including grains, total dairy, legumes, meat, processed meat, total vegetables, starchy vegetables, fruits, nuts, sugars,  Although the P-value of sweet snacks and starchy vegetables were significant (Table 3), the OR and CI did not confirm a positive correlation (Table 4).  Data are mean ± standard deviation *Mean daily intake of energy, macronutrients and fiber were compared between MS and control using independent sample T-test   Several mechanisms have been proposed to explain models(10grams/day) ‡ Adjusted for energy(Kcal) § Additional adjustment for Body mass index(BMI) (kg/m2), sex(male, female), family history of multiple sclerosis(yes, no) vitamin D supplementation before onset of disease(yes, no), city they lived in the first 15 years of life(arid, humid, snow), total energy (kcal), total fibers(grams) and total fat (grams)  which the outcome was compared to several daily recalls in a previous study (17). Although small sample size and case-control sets are considered as weaknesses of the current study, use of a validated semi-quantitative FFQ for dietary assessment and use of several statistical models with adjustment of potential confounding variables were the strengths of this study.
In conclusion, a positive association was found between dietary intake of processed and nonprocessed meat with the risk of multiple sclerosis in the patients of our study.